1. Field of the Invention
The present invention relates to a shoe device secured to a syphon for removing condensate.
More specifically, the present invention relates to a shoe device secured to a syphon for removing condensate from an internal surface of a rotating cylinder.
2. Background Information
The present invention provides an apparatus for removing fluids from a rotating drying cylinder such as but not limited to cylinders used for the drying or cooling of paper. The apparatus consists of a stationary syphon with a fluid passage extending from a position adjacent to the inside surface of the rotating cylinder roll, through a syphon pipe fluid passage that extends from the inside of the rotating cylinder roll, through a hollow journal of the rotating cylinder, and to a rotary joint connected to external stationary piping.
The invention more specifically provides a stationary syphon shoe that is positioned at the end of the fluid passage, adjacent to the inside surface of the rotating cylinder. This syphon shoe is radially adjustable so as to position the stationary syphon with a predetermined gap to the inside surface of the rotating cylinder roll. With suitable pressure differential or cylinder roll rotational speed, the syphon shoe will act to collect condensate from the inside surface of the dryer cylinder and direct the condensate out of the cylinder through the fluid passage. The stationary syphon shoe is supported by a vertical syphon pipe that holds the syphon shoe rigidly above the inside surface of the cylinder and serves as the fluid passage. Typically, the vertical syphon pipe in the prior art is most often a stainless steel pipe. Stainless steel is not susceptible to erosion and corrosion from the action of hot condensate flowing through the pipe. The syphon shoe, according to the present invention has a soft tip facing the inside dryer cylinder roll surface. This soft tip will not damage the dryer if the two come into direct contact. This is a primary object of the present invention. The syphon shoe is constructed such that the radial thickness of the soft tip is larger than 25 mm and preferably larger than 50 mm, such thickness being measured from the radially outermost end to the portion of the syphon shoe that is metallic. The rotating cylinder is used primarily to dry paper, but also can be used for drying, heating or cooling foodstuffs, textiles, and the like, as they pass over the outside surface of the rotating cylinder.
Conventional stationary syphons are either cantilevered from the external rotary joint or are supported by brackets that are either bolted to the dryer journal or to the inside surface of the dryer head. Occasionally, the stationary syphon shoe comes in direct contact with the dryer shell. With conventional stationary syphon shoes, the surface of the rotating dryer shell can be damaged by this contact. This damage can be so severe that the dryer cylinder must be removed or replaced. To minimize the potential for damage, the syphon shoe of the present invention has a soft tip. This soft tip is held in position by a metal clamp pad to the vertical syphon pipe. The soft tip will not damage the inside surface of the cylinder if the two come into direct contact. The clamp pad, on the other hand, would be capable of damaging the shell, so in the present invention, the clamp pad is positioned entirely above the radial outermost end of the vertical syphon pipe. The primary advantage of this invention over the various prior art syphon shoes is the elimination of potential damage to the inside surface of the shell.
Wet paper webs are dried by a series of metal rolls in the paper making process. These rolls are heated by steam that passes through a rotary joint, through the roll journal, and into the inside of the metal roll. The steam is supplied to the rotary joint from fixed, that is, stationary, piping. The steam then goes through the journal of the roll. Once inside the roll, the steam condenses as it transfers its heat to the inside surface of the roll. The condensed steam, that is, water or “condensate”, must then be removed so that the roll does not fill up with water. The water is removed through a pipe called a “syphon” by flowing into the syphon pipe, up to the center axis of the roll, and then out of the roll through the syphon pipe that extends through the roll journal. Syphons either turn with the roll, that is “rotary” siphons, or remain fixed with the joint, that is “stationary” syphons.
Stationary syphons that are used to remove condensate are attached to a stationary portion of the rotary joint in order to prevent the syphon from rotating and to seal the inlet flow of steam from the outlet flow of condensate and blow through steam. Conventional stationary syphons are mounted in one of three ways. The most popular method is to use a large cantilevered support tube mounted in the rotary joint and extending through the dryer journal and into the dryer roll. The cantilever tube supports the syphon pipe that extends from the dryer axis to the dryer shell. The tube is stiffer and stronger than standard pipe and can bear the required weight loads and other forces.
The second method of supporting the stationary syphon is to use a large cantilevered support tube that is mounted to the outside end of the journal. The rotary joint can be mounted either to the end of the dryer journal or an external support. In this configuration, the condensate pipe is attached to a stationary portion of the rotary joint and extends through the support tube to the inside of the dryer cylinder. The tube supports the stationary syphon pipe on the inboard end of the support tube, inside the cylinder, typically with carbon bushings. The support tube is larger in diameter, stiffer, and stronger than the condensate pipe and is therefore capable of supporting the syphon weight and associated loading.
The third method of supporting the stationary syphon is a bracket support that is mounted inside the roll where the journal bore terminates inside the roll. The rotary joint can be mounted either to the end of the dryer journal or an external support. In this configuration, the condensate pipe is attached to a stationary portion of the rotary joint and extends through the support tube to the inside of the dryer cylinder. The bracket supports the condensate pipe at the end that is located inside the dryer. The bracket is mounted close to the inboard end of the pipe, to give it proper support. The bracket spins with the roll while the condensate pipe remains stationary, that is, the pipe is not rotating. Carbon graphite or equivalent bushings are used in the bracket to allow relative motion between the bracket and the condensate pipe. The bracket is stiffer and stronger than the condensate pipe and supports most of the loading.
In each of these prior art stationary syphon designs, the radial syphon pipe extends to and is positioned close to the inside surface of the dryer cylinder. To improve the collection of condensate, a special syphon shoe is connected to the end of the vertical syphon pipe, adjacent to the inside surface of the cylindrical roll. This syphon shoe is generally contoured and set so that there is a natural “scoop” action to entrain condensate that is in a rimming condition. The syphon shoe is generally positioned very close to the roll surface, in order to prevent large amounts of condensate from accumulating inside the roll.
Syphon shoes of the prior art have been manufactured from stainless steel castings. The stainless steel does not erode or corrode in service, and hence has provided long service life. There is, however, an increased risk that the stainless steel shoe will damage the inside surface of the cylindrical roll, if they come into contact with each other.
On occasion, however, the support for the stationary syphon pipe is damaged or fails, or for various reasons is displaced from its intended position on the inside of the journal of the roll, such that the syphon shoe contacts the inside surface of the roll. Stainless steel syphon shoes tend to harden when they contact the rotating metal cylinder surface. The hardened stainless steel tends to wear and cut into the cylinder surface, eventually damaging the cylinder, possibly to the point of failure.
To prevent such damage in the event of contact, stationary syphon shoes of the prior art design have alternatively been made from fully-annealed ductile iron or gray iron castings. These materials, however, tend to erode and corrode in service. Yet another prior art solution has been the use a syphon shoe that consists of a metal clamping portion and a soft non-metallic tip adjacent to the dryer surface. In this prior art design, the soft portion of the syphon shoe does not damage the roll surface on contact, but after the soft portion is worn away, the metallic clamping portion can contact the surface and can damage the surface.
The object of the present invention is to have a stationary syphon shoe that can be rigidly positioned in close proximity to the inside surface of a rotating cylinder, with little potential for the syphon shoe to damage the roll surface should they come into contact with each other.
The syphon shoe according to the present invention consists of a stainless steel clamp pad and a soft non-metallic tip. The stainless steel clamp is used to hold the syphon shoe to the stainless steel radial syphon pipe. The tip of the syphon shoe is made from a material that is softer than the inside surface of the roll, a material that does not readily corrode or erode, and one that ideally maintains its rigidity and strength at high operating temperatures.
In the preferred embodiment of this invention, the soft material is PTFE (TEFLON)
The clamp pad according to the present invention holds the syphon shoe to the radial syphon pipe with the entire metallic portion of the clamp being positioned above the end of the stainless steel syphon pipe which means the clamp is radially closer to the roll axis of rotation than the distal end of the syphon pipe.
With the preferred embodiment of the present invention, the soft portion of the syphon shoe can contact the inside surface of the rotating cylinder and experience significant wear, without having the metallic portion of the syphon shoe contacting the roll. In this embodiment, the soft portion of the syphon shoe can wear down until the radial syphon pipe is contacting the inside surface of the cylindrical roll, and yet the metallic portion or clamp portion of the syphon shoe is still not touching or damaging the shell.
The concept of the present invention allows the maximum amount of space between the radial syphon pipe as a wearing allowance, without having any metallic portion that extends below the end of the syphon pipe.
With the preferred embodiment of the present invention, the metallic clamping portion of the syphon shoe is, in operation, entirely above the end of the syphon pipe. The soft portion of the syphon shoe extends from the metallic portion toward the inside surface of the rotating cylinder. The soft tip can contact the inside surface of the rotating cylinder and experience significant wear, without having the metallic portion of the syphon shoe contacting the roll. In this embodiment, the soft portion of the syphon shoe can wear down until the radial syphon pipe is contacting the inside surface of the cylindrical roll, and yet the clamp or metallic portion of the syphon shoe is still not touching or damaging the shell. The thickness of the soft tip is at least 25 mm when measured radially from the portion closest to the cylindrical roll surface and is ideally 50 mm or more.
Further, the front face of the soft tip has an angled profile and a radius that minimizes the impact force of rotating condensate on this face of the stationary syphon shoe, to minimize the forces on the syphon support assembly.
Still further, the bottom of the syphon shoe, that is, the portion facing the surface of the rotating cylindrical roll, has a radius that matches or nearly matches the inside radius of the roll. Still further, the radius of curvature of this surface has its center located offset from the centerline of the radial syphon pipe and still further this offset is located circumferentially on the opposite side of the axis of the radial pipe from the leading end of the syphon shoe.
Moreover, the back face of the syphon shoe, that is the portion opposite the front face, consists of a contour that is generally rounded so as to produce minimal disruption of the condensate that flows around or under the syphon shoe.
The present invention provides an apparatus for removing condensate from the inside of a rotating cylindrically roll such as a drying cylinder of a papermaking machine and the like. The apparatus includes a stationary syphon shoe located near the inside surface of the rotating cylinder shell and connected by a syphon pipe that extends from the syphon shoe through a hollow journal of the cylinder to a rotary joint located outside the cylinder. The syphon pipe is supported by a suitable cantilevered horizontal support tube, an internal bushing in an internal bracket, or an internal bushing in a journal-mounted support tube. The syphon shoe has a soft tip which is characterized by the following:
1. The thickness of the soft tip is at least 25 mm and preferably more than 50 mm.
2. The soft tip extends radially above the radially outermost end of the vertical syphon pipe.
3. The soft tip is attached to a clamp pad with a “T” slot or equivalent mounting.
4. No metallic portion of the clamp pad extends below the radially outermost end of the vertical syphon pipe.
5. The front face of the soft tip has a radius and/or an angled profile so as to minimize the impact forces of the condensate on the syphon assembly.
6. The back face of the soft tip is contoured so as to minimize the disruption of the flow of condensate around or under the syphon shoe.
7. The bottom face of the soft tip has a radius so as to approximate the radius of the inside surface of the cylindrical roll.
8. The center for the bottom face radius is located offset with respect to the centerline of the vertical syphon pipe.
9. The center offset point is located on the circumferentially opposite side of the soft tip front face.
Thus the primary feature of the present invention is to provide a shoe device secured to a syphon that prevents any damage to an internal surface of a cylinder.
Another important feature of the present invention is to provide a shoe device secured to a syphon for extracting condensate from a dryer cylinder of a papermaking machine.
A further important feature of the present invention, is the provision of a shoe device secured to a syphon such that even if the shoe device becomes worn down, the syphon clamp of the shoe device will not contact and damage the internal surface of a dryer cylinder
Other features and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description of a preferred embodiment of the present invention contained herein.